Circuit controlling device



Aug. 7, 1945. v. N. REIFF CIRCUIT CONTROLLING DEVICE Filed July 13, 1942 INVENTOR- M 71.. (o r Patented Aug. 7, 1945 2,381,688 omcorr CONTROLLING nnvron Vincent N. Reifl, St. Marys, Pa.,"a's signor to Stackpole Carbon Com pany, St. Marys, Pa a corporation of Pennsylvania Application July 13, 1942, Serial No. 450,683

3 Claims. (Cl. 2006) This invention relates to electrical control de-. vices for radio circuits and the like, such as volume controls and switches, and more particularly to the control shafts by which they are actuated.

The control shafts of radio switches, volume controls, and the like extend through the front panels of the sets and are rotated by means of knobs mounted on their outer ends. The diameter of the control shafts have been, for-the most part, standardized at one-quarter of an inch, but there is no standard for the type of shaft end to which the actuating knob is connected. Consequently, there are several diiferent types of shaft ends with each type fitting a different type of knob. For example, some control shafts have a knurled end that is bifurcated to give it resiliency. This is merely forced into a knob provided with interior ridges or teeth that cooperate. with the knurls to prevent the knob from turning on the shaft. Other shafts have plain ends or ends with.

a flattened side portion, and the knob is rigidly mounted on the shaft by means of a set screw carried by the knob. The flats on these shafts are not all the same, so that a set screw in a given knob may not engage the flat on every type of shaft. The result of all this has been that when a control unit was replaced in a radio set it was not possible to use the original knob unless the control shaft on the new unit had an end that would fit the old knob. Therefore, a control unit having the right type of shaft had to be found or else the set came to have knobs that did not match, which is objectionable in many cases. A further disadvantage of such practice is that the old shaft generally is discarded, which is an undesirable waste of metal, especially in times of war when there is a serious shortage of metals.

It is among the objects of this invention to provide an electrical control device with a control shaft which conserves metal, which can be readily connected to substantially any type-of knob used with such devices, and which can be easily and effectively connected to an old control shaft separated from the device it operated.

In accordance with this invention, the circuitcontrolling means of an electrical control device is actuated by a rotatable shaft that is so short as to be no more than a stub shaft which is too short to project through a radio set panel or the like. To lengthen the stub shaft and for the purpose of this invention its outer end is provided with means for detachably connecting it to one end of a separate short shaft the opposite end of which is formed for carrying a knob by which the shaft is turned. Thus, the conventional long shaft that is used with any control device that is to be replaced can be cut off and then rigidly connected, with the original knob attached, to the outer end of the stub shaft of the unit that is used for replacement. Preferably, the two shafts are connected by means of a socket member secured to the outer end of the stub shaft for receiving and frictionally gripping one end of the knob-carrying shaft. The socket may be provided with a slot to give it resiliency, while a set screw threaded in its side wall may be used to make the connection stronger.

The preferred embodiment of the invention is illustrated in the accompanying drawings in which Fig. l is an enlarged side view of a combined volume control and snap switch, partly broken away to show the interior of the unit; Fig. 2 is a horizontal section taken on the line Ill-II of Fig. 1. and showing a stop lug in operative position; and Fig. 3 is a view similar to Fig. 2 with the stop lug removed so that the switch is turned off.

Referring to the drawing, an insulating base I I is provided with a central opening from the bottom of which a threaded bushing 2 projects. Rotatably mounted in this bushing but projecting only a very short distance below it is a stub shaft 3 provided at its outer end with a socket member 4 that will be referred to in greater detail later. Mounted on the base member is an electrical resistance element 5 encircling the portion of the control shaft projecting above base I. On the inner end of the shaft there is a rectangular insulating member 6 provided in its opposite ends with notches l. The bottom of this member is engaged by the body of a metalcontact member having upturned lugs B that project into the notches so that the contact member will be turned by member 6. The central portion of the contact member is spaced from the control shaft. Projecting toward each other from the ends of the contact member body is a pair of spring contact fingers 9 having downturned ends that engage and slide upon the resistance element. Terminal members III are connected to the opposite ends of the resistance element whilean intermediate terminal member II is electrically connected to the contact member, preferably by means of a resilient wire l2 (Fig, 1) coiled around the control shaft beneath the contact member to which it is attached. Thi gives a positive electrical connection regardless of the position of the contact member.

The insulating member 6 is rigidly connected to the control shaft, and the rotation of the contact member is limited, through the medium of a rigid arm l6 tightly clamped against member 6 by the upset inner end of the shaft. At one side of member 6 this arm has a pair of laterally spaced upturned ears ll that engage one side or the other of a detent l8 pressed in from the side of the metal control housing l9 to limit the rotation of the control head in both directions. Arm [6 is provided on the opposite side of memger has ears that are adapted to receive between them the switch-actuating projection Is by which the trigger is swung on its pivot 24 to turn the switch on and off. The trigger is so mounted that projection I9 has transient engagement with it.

As shown in Fig. 3 a small rectangular opening 3| is punched in the side wall of the volume control housing l9 near detent l8, and, as shown in Fig. 2, a tongue-like metal lug 32 is mounted in this opening. The lower end of the lug is spot welded to the outside of the control housing below opening 3|. The upper portion of the lug extends through this opening and projects into the path of movement of one of the ears l1 on arm i6 and thus limits or stops the movement of the contact member and of the related parts that rotate with it as they are moving toward switch-opening position. The position of the lug relative to detent I8 is such that it stops the switch-actuating projection 20 just as it reaches the switch trigger but before it can move the trigger. Therefore, the switch remains in either 017" or on" position, depending on which side of detent I8 the lug' is located on, regardless of the position of the contact member, and in so far as operation is concerned might just as well as be absent. The volume control thus operates as smoothly as a volume control without a switch.

In case this unit is used for replacing a similar combined unit so that it is necessary to use the switch for its intended purpose as a circuit breaker, the lug 32 is mounted so that it can be removed from inside the housing. For this purpose the portion of the lug inside of the control housing is doubled back on itself with the upper endextending back out through opening 3|. To render the lug inoperative, its projecting upper end is gripped by pliers and pulled until the lug either is out of the way of projection IT or is entirely outside of the housing. If desired the lug can be twisted off the housing and discarded. As the movement of the contact member and switch-actuating projection 20 no longer is restrained by the lug, the projection 20 can travel far enough to snap the trigger. The unit is thenv the same in construction and operation as the conventional combined volume control and switch.

It is a feature of this invention that my control device can be used with control knobs of various types that would not all fit the same con-- trol shaft. This is one of the reasons why the socket member 4 is provided on the end of the stub shaft 3. The socket member preferably is formed by a cylindrical metal sleeve into one end of which the outer end of the cylindrical stub shaft is inserted a short distance as shown in Fig. 1. The sleeve and stub shaft may be secured tightly together in any suitable manner, such as by a drive fit. The socket thus formed in the outer portion of the sleeve has the same diameter as a standard control shaft. When it is desired to replace with this device a similar control unit, the control shaft of the latter is cut of! at the correct length with a hack saw or the like and the severed end of the knob-carrying portion 26 is then inserted in the socket 4. The control knob, indicated in broken lines in Fig. l, of the original unit is thus connected to the new control unit by means of the old shaft 26. It will be understood, of course, that my control devices are furnished without any shaft inserted in the outer end of the socket member, and that the knob-end of the old shaft 26 may be of any type.

To rigidly connect stub shaft 4 and old shaft 26 together the side wall of the socket preferably is provided with an inwardly extending slot 21 that permits the socket to yield slightly when shaft 26 is forced into it and to frictionally grip the shaft and prevent it from turning in the socket. The grip thus obtained has been found ample to prevent relative movement of the two parts of the shaft when the device is operated. Nevertheless, to provide for a situation in which the knob-carrying shaft might be slightl undersize so that the socket would not grip it tightly enough, the side wall of the socket can be provided with a set screw 26 extending therethrough and tightened against the side of the shaft in the socket.

By making use of the old control shaft off the unit that is replaced by my unit it is unnecessary for my unit to be provided with the usual shaft that is long enough to extend through the panel of the set with which it is used. Because of this feature considerable metal can be saved, for control units such as these are used by the millions.

According to the provisions of the patent statutes, I have explained the construction and operation of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, Within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

I. An electrical control device for radio circuits and the like, comprising circuit-controlling means, a rotatable stub shaft for actuating said means, and a socket member secured to the outer end of the stub shaft for receiving and frictionally gripping one end of a removable knobcarrying shaft for detachably connecting them together.

2. An electrical control device for radio circuits and the like, comprising circuit-controlling means, a rotatable stub shaft for actuating said means, and a socket member secured to the outer end of the stub shaft for receiving and frictionally gripping one end of a removable knobcarrying shaft for detachably connecting them together, the side wall of the socket being provided with an inwardly extending slot to impart resiliency to the socket member.

3. In combination, a rotatable stub shaft for actuating electric circuit-controlling means, a sleeve partly telescoped over the outer end of the stub shaft and rigidly mounted thereon to form a socket, a removable shaft having its inner end inserted in said socket, the socket-forming portion of the sleeve frictionally gripping said inner end of the removable shaft whereby to rigidly connect it to the stub shaft, and a control knob rigidly mounted on the outer end of said removable shaft for turning it.

VINCENT N. REIFF. 

